1. Field of the Invention
The present invention relates to signals, in particular, Light Emitting Diode (LED) Signals. More specifically, the present invention relates to LED signals using a novel optical element to control the light distribution of a small LED light source.
2. Description of the Related Art
LED signals such as LED traffic signals, present numerous advantages over incandescent lamp traffic signals. Use of LEDs provides a power consumption savings and extremely long life compared to incandescent light sources. The long life span of the LED signals leads to improved reliability and lower maintenance costs.
Due to the large number of existing incandescent traffic signals, most LED signals are designed to be retrofit into existing systems originally designed for incandescent lamps. To allow an easy retrofit without requiring significant changes to the preexisting AC power distribution and logic circuits, then LED signal assemblies typically incorporate a power supply to drive the LEDs at a lower, controlled, direct current power level.
Typical LED signals use multiple LEDs to replicate the light output of the incandescent lamp. Multiple LEDs can create a display aspect within which the individual points of light from each LED are discernable. This is undesirable. LED technology is improving. Each generation of LEDs is brighter, requiring fewer LEDs to meet the intensity specification. While fewer LEDs lowers the cost of the signal, it also increases the potential for viewing the LEDs as individual point sources and for having undesirable shadows. To combat this, the present invention utilizes a novel optical element.
Prior art LED traffic signals control the light distribution by using one of three methods: LEDs alone; by combining LEDs with a spreading or distributive cover; and most commonly by collimating the light from the LEDs and then distributing or spreading the collimated light. The spacing and placement of the LEDs is also important to controlling the light in the prior art systems as the optics of prior art systems are dependent on the spacing and placement of the LEDs.
The inventive optical element provides distribution before collimation and is more efficient than prior art methods for LEDs with wide radiation patterns. The signal of the present invention is also more flexible because all the optics are in one part. The light distribution can be changed by changing the optical element. In prior art systems having both a fresnel lens and a distributive cover/shell are used to control the light, changing the light distribution requires changing both the lens and the cover/shell. It is not necessary to also change the shell/cover.